Generally, DRM is a technology for securely protecting and systemically managing rights object of digital contents, and provides a series of protection and management systems relating to illegal copy of digital contents, acquisition of rights to use the digital contents, and procedures of use of the digital contents.
FIG. 1 illustrates a general DRM system.
The general DRM system controls digital contents provided from a contents provider to a user to allow the user to use the digital contents as much as rights object (RO) granted to the user. At this time, the contents provider is an entity corresponding to a contents issuer (CI) and/or a rights issuer (RI).
The contents issuer issues contents (hereinafter, referred to as “DRM contents” (or digital contents)) protected using a specific encoding key to protect the DRM contents from users having no right to access them, and issues rights object required to use the DRM contents.
A DRM agent provided in a terminal receives the DRM contents and rights object from the contents issuer and the rights issuer, and controls use of the DRM contents in a corresponding terminal by analyzing permission and/or constraint included in the rights object.
Generally, since the rights object is encoded by a public key of a specific terminal, terminals other than a terminal having a private key corresponding to the public key cannot decode and use the DRM contents related to the rights object.
For this reason, a problem occurs in that terminals other than a specific terminal to which the rights object has been issued cannot read out the DRM contents from the memory card (that is, SRM can be called) if the rights object and the DRM contents related to the rights object are stored in a portable memory card (SRM) such as a multimedia card in the general DRM system.
Also, since the rights object has issued to the specific terminal in the general DRM system, if the rights object and the DRM contents related to the rights object are stored in the memory card, only the specific terminal to which the rights object has been issued can read out the DRM contents and the rights object from the SRM. For this reason, a problem occurs in that utility of the SRM is deteriorated.
Moreover, a problem occurs in that the SRM cannot have its own rights object because the contents provider cannot issue the rights object of the DRM contents to the SRM in the general DRM system.